This invention relates to a medical vacuum regulator and, more particularly, to an electrical medical vacuum regulator in which regulation control is by electrical means.
Medical vacuum regulators of the type which employ mechanical regulators are well known as illustrated by such a regulator shown in U.S. Pat. No. 4,903,726 of Martin et al. issued Feb. 27, 1990, and the other regulators shown in references cited therein. Generally, such mechanical regulators have pneumatic valves with mechanical feedback systems which enable them to control the opening and closing of the valve for respectively coupling and decoupling a patient vacuum delivery system, or patient, to a source of unregulated vacuum. Regulation of vacuum to the patient at a preselected vacuum level is thereby achieved mechanically. These mechanical regulators have been used in conjunction with solenoid on/off control valves to intermittently apply the regulated vacuum to the patient and, thus, to a degree are considered electrically controlled regulators. However, the actual vacuum regulation in these electrical regulators is achieved solely through mechanical means of well known construction. Thus, while it has been easy to intermittently connect and disconnect the regulated vacuum to the patient through means of electrical control, and to employ electrical displays of operation parameters, it has not been known to regulate the actual level of vacuum except by manual manipulation of the pneumatic valves, themselves. This has caused electrical control of regulation levels on other than an on and off basis to be difficult if not practically impossible.
The patient delivery system generally includes an elongate plastic tube which is connected at one end to the outlet port of the regulator and at the opposite end to a sealed collection bottle. The sealed collection bottle, in turn, has an inlet connected to the patient through means of a flexible draw tube inserted into a body cavity of the patient, such as the stomach. The vacuum in the inlet tube causes body fluids to be drawn into the distal end of the draw tube in the body cavity, through the draw tube and into the collection bottle. It is common for the distal end of the draw tube within the body cavity to be adjacent or actually touching delicate tissues. Accordingly, a difficulty with this operation in known mechanically controlled regulators is that the initial surge of vacuum at the beginning of each time period of vacuum can move the distal end of the draw tube into the body cavity and thereby cause injury to the surrounding tissue. With continuous operation, the draw tube is more susceptible to blockage, but sometimes the additional strength of continuous vacuum is required. Thus, this operation continues to be employed despite the possible risk of injury to the patient, and such injuries continue to occur with known medical vacuum regulators.
Reliability is an important feature for medical vacuum regulators to possess, since the loss of vacuum source can be catastrophic for the patient. The vacuum pump motor is perhaps the most vulnerable element of the system. However, in known regulators, virtually no efforts have been made to maximize the useful life of the pump motor. In particular, in known medical vacuum regulators, the pump is forced to operate against a load which is inverse of the patients needs. If the patient needs low vacuum, the pump sees high vacuum. The pump is forced to operate against the maximum load when the patient is vented to atmosphere. This results in excessive wear on the vacuum pump motor and directly reduces reliability of the entire vacuum system of which the regulator is a part.
Another difficulty with known medical vacuum regulators which selectively operate in intermittent and continuous modes is that in the event of temporary power failure, unless mechanical switches are used that are unaffected by power failure, it is possible for the known regulators to come back to service when power is restored in a mode of operation which had not been prescribed for the patient. Such a result can be traumatic to the patient, but medical vacuum regulators with electronic mode selection switches are not provided with means for preventing such a result.